Acetyl CoA carboxylase (ACCase) catalyzes the first committed step in fatty acid biosynthesis and has also been chemically validated as an herbicide and fungicide target. Structurally, ACCases are biotinylated, multifunctional enzymes comprised of three domains: a biotin carboxylase domain, a biotin binding site, and a carboxytransferase domain. In prokaryotic ACCases, as well as in the plastidic isoforms of most plant ACCases, the three domains reside on three distinct, dissociable proteins. In contrast, in most eukaryotic ACCases the three domains reside on a single polypeptide of 160 kD to 280 kD. In their native state, the eukaryotic enzymes are typically dimers or tetramers ranging in size from approximately 400-800 kD.
The ACCase reaction takes place at two catalytic sites via two partial reactions: the ATP dependent carboxylation of the enzyme-bound biotin prosthetic group, and the subsequent transfer of the carboxyl group from biotin to acetyl CoA to form malonyl CoA. The natural product soraphen has been demonstrated to be a broad-spectrum fungicide that acts by inhibiting the biotin carboxylase reaction of ACCase. ACCase's are known to be low abundant and labile proteins. These properties impede the identification of new ACCase inhibitors.
The present invention provides a peptide comprising a biotin carboxylase domain and fragments thereof useful for the identification of Acetyl CoA carboxylase inhibitors, which in turn are useful among other things as fungicides, insecticides, nematicides, herbicides and pharmaceuticals.